Deprecate KDE4 software, categories www-x11-themes

This is the last bit.

The last upstream release supporting KDE4 was 10 months ago,

https://www.kde.org/announcements/announce-applications-17.08.3.php ,

and the kde@ team for FreeBSD has supported modern KDE (i.e. KDE
Frameworks, Plasma 5 and KDE Applications) for 4 months. Give a 4
month deprecation period to allow users to switch over.